Battery Cell Phase-Shift Detection for Early Defect Warning
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Solution Overview
Problem
Current methods for detecting cell damage in high-voltage batteries, such as those used in motor vehicles, are inadequate for early detection of defects, particularly thermal propagation, and are susceptible to interference, requiring significant energy and time, and do not allow for timely warning of potential hazards.
Innovation Solution
A method using differential impedance spectroscopy to measure the phase angle difference between cells in a battery, evaluating only the imaginary components of cell resistances, which is less susceptible to interference and allows for early detection of cell defects by measuring phase shifts in alternating voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance spectroscopy is used to determine internal cell temperature, then measurement precision is improved, but use of energy increases and device complexity increases
Solution Approach 1:
The patent applies partial impedance spectroscopy by measuring only the imaginary component of cell impedance at a single frequency (13 Hz) rather than performing a full frequency sweep. This partial measurement approach maintains sufficient precision for detecting thermal propagation while dramatically reducing energy consumption and measurement time
Solution Approach 2:
The patent changes the measurement parameters from a full frequency spectrum analysis to a single-frequency measurement at 13 Hz, which corresponds to the relaxation frequency of the electrolyte. This parameter change enables early detection of cell degradation while minimizing energy requirements
2Measurement precision
If full impedance spectroscopy with frequency sweeping is used, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs a partial impedance measurement at a single critical frequency (13 Hz) rather than sweeping through the entire frequency spectrum. This allows rapid detection of cell state changes while completing measurements in seconds rather than minutes
Solution Approach 2:
The patent performs measurements at the predetermined frequency of 13 Hz, which is known to correspond to the electrolyte relaxation frequency. This preliminary identification of the critical frequency allows direct detection of cell degradation without time-consuming frequency sweeps
3Device complexity
If traditional temperature measurement methods are used, then device complexity is reduced, but measurement precision deteriorates due to time delay
Solution Approach 1:
The patent replaces mechanical/thermal measurement methods (temperature sensors) with electrical impedance measurement. This substitution enables non-contact, real-time detection of cell internal state changes without the time delays inherent in thermal conduction to external sensors
Solution Approach 2:
The patent uses impedance spectroscopy as an intermediary measurement method that indirectly detects internal cell temperature and degradation states through electrical properties. This intermediary approach allows detection without direct thermal contact, eliminating the time delay between internal heating and external sensor detection
4Ease of operation
If conventional voltage measurement is used, then ease of operation is maintained, but measurement precision deteriorates due to susceptibility to interference
Solution Approach 1:
The patent changes from measuring only voltage magnitude to measuring the phase angle of the impedance response. This parameter change provides information about the imaginary component of impedance, which is sensitive to cell degradation and thermal propagation while being less susceptible to common electrical interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables early detection of cell defects, reduces the risk of thermal propagation, and provides timely warnings with minimal energy consumption and resistance to vehicle electrical system interference.
Implementation Method 1
One method for determining the internal cell temperature is called impedance spectroscopy. In impedance spectroscopy, the phase relationship between current and voltage is evaluated to determine the real and imaginary parts of a cell's resistance.
Data Source
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AI summary
The invention relates to a method for determining a state of at least one cell (1, 2, 3) of a battery (4), wherein the battery (4) has a plurality of cells (1, 2, 3), which are connected in series with each other, the method comprising at least the following steps: a) applying an alternating current (5) to the plurality of cells (1, 2, 3); b) measuring the alternating voltage (6, 7) produced thereby at at least a first cell (1) and a second cell (2); c) analyzing a phase position (8, 9) of the measured alternating voltage (6, 7) of each cell (1, 2); wherein a difference at least between a first phase position (7) of a first alternating voltage (6) measured at the first cell (1) and a second phase position (9) of a second alternating voltage (7) measured at the second cell (2) forms a conclusion about a difference between the states of at least the first cell (1) and the second cell (2).